Red litmus turns blue in a solution, and after adding acid both red and blue litmus show no change. What is the nature of the final solution?
Answer and explanation
Correct answer: Neutral
Initially, red litmus turning blue shows that the solution is basic, because hydroxide ions change the indicator colour. When acid is added in sufficient amount, its hydrogen ions neutralise the hydroxide ions: H⁺ + OH⁻ → H₂O. If the final solution changes neither red nor blue litmus, it is approximately neutral. A strongly acidic or basic solution would still change one indicator.
Frequently asked questions
What is the correct answer to this question?
Neutral
Why is this the correct answer?
Initially, red litmus turning blue shows that the solution is basic, because hydroxide ions change the indicator colour. When acid is added in sufficient amount, its hydrogen ions neutralise the hydroxide ions: H⁺ + OH⁻ → H₂O. If the final solution changes neither red nor blue litmus, it is approximately neutral. A strongly acidic or basic solution would still change one indicator.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
